turbo blue

well, first of all i drive a 93 rx7. this isn't really a question, but rather an idea. i am somewhat new to rotaries but really familiar with the function and downsides, just new to owning one. most of my experience comes from high horsepower piston engine building and tuning. my idea was, i hear a lot about people having housing coolant seal failures. i know on higher horsepower piston applications you can run a copper crush ring in a machined groove around the combustion chamber to create a super strong seal for high boost and pressure. i was wondering if maybe the rotary engine builders have tried to use a copper crush ring instead of the crappy failure prone rubber like coolant seals they use now. i know you can make the top end of a piston engine bullet proof, and maybe there could be some research and testing of a soft copper ring or a rubber coated copper ring in place of these soft all rubber coolant seals. we already have the machined groove, just using a prehistoric sealing device in a high heat burning environment. every time i get in my rx7 i cringe at the thought of a complete overhaul because of a stupid rubber seal.

comments on this anyone?

B6T

iTrader: (2)

Great idea. However I would think that it's a lot easier to seal a round cylinder and get an even seal with a copper ring then it would be to seal the housings in a rotary. Remember that you're missing a few tension bolts around the port area, and because of this and not having equally spaced bolts, I it would think it would create a spot where the housings could lift/separate slightly (under the kinda pressures you'd be running to require a copper ring) and blow the seal.

I bet someone has tried this before...

turbo blue

thats why you make the seal a really maleable alloy of copper which can still take the heat but will be soft enough to conform to the housings. some piston engines have an odd head bolt pattern not symetrical with the cylinder and they work flawlessly. i think there is more than enough tension on the sandwich to properly crush such a seal but i don't have the time nor the funds to try something of this calibur. it might even be a good idea to put a really thin rubber coating on the copper core like on some of the high end multi layer steel headgaskets. the copper will conform to any imperfections in the machined groove and the rubber coating will take up any little slack there is to be had.

GTRay

the problem is that the failure isn't just the coolant o-ring. When you lose an o-ring it is because the casting around the o-ring failed. almost all failures occur in the same location. The failure point is generally a spot that gets very hot on a regular basis. if there is any type of weakness in this area the casting will fail. once the casting lets go the seal won't stand a chance.

http://rotaryresurrection.com/rotary...naldamage.html

That site should demonstrate what i'm trying to explain. i'm sure an alloy seal is something that mazda engineers tried at some point in development and figured out it wasn't very effective in stopping motor failure from overheating or water jacket failure.

Ray

ronbros3

Sounds like an idea, try it ,it might just work, remember the inner seals combustion pressure, and the outer seals coolant. part of the reason for a soft seal is all the plates and housings have to be flat against each other, if not then misalignment can cause E-shaft bearing problems, and the rotors touching the side plates. by the way as simple as a rotary is, it has encredible technology in it, remember the simpler somthing is the more complex it becombes.!! anyway dont let me change your ideas, GO FOR IT !!! Ron

ronbros3

Last but not least there are some very good seals out there, one that has been used in F1 was a hollow seal, filled with nitrogen gas, starts to give some ideas!! yeah! go for it ,,, dont I wish i had R&D money.

turbo blue

well no joke, its mr. ron brothers. this is matt, from daytona. used to work at projekt 7. i finally got rid of the 240 for something a little less modded. too much horsepower and not enough money to fix the things it liked to break. anyway, nice to see you are still at it. hows the turbo II hanign these days. i miss that thing, and the jag. too bad i had to move back to nc. the car i got came with a parts car that has the complete drivetrain (no i won't part out, has a 5 speed conversion in it) and engine. i might take that engine apart and rebuild it as a spare and maybe do some research on a hard seal for the housings. i would come up with a way to assemble part of the motor (like one iron and one rotor housing) and check the clearence with different types of seals to make sure the housings stay true and don't have an angle from a piece of copper seal thats not crushing correctly. my only question is will i warp the iron or the rotor housing if i torque just a partial assembly together. if so, i KNOW for a fact you have shelves and shelves of them. maybe you could toss that around in your garage and see if it works. anyway, just a thought.

RETed

You're only as strong as the weakest link in the chain...

Yes, piston motors can "o-ring" the block, but what does this do?
It can shift the weak point to somewhere else.
So there's your problem.
So you just made the o-ring stronger...
It's going to fail somewhere else.

As GTRay mentioned, the thin wall of the o-ring grooves tends to fail pretty easily too.
If not, it's going to fail somewhere else.

Making the o-ring stronger is not how I would approach it.
I would 1) make sure your cooling system is bulletproof, and 2) tune the car as safely as possible.


-Ted

turbo blue

from what i have understood coolant seals are the weak link in the cooling system. and the rotor seals are the weak link in the combustion department. so i don't see how i can create a weak link by strengthening the coolant seals if they aren't what takes a dump when you detonate. i know you can get wear on the casting which allows the coolant seal to be extruded through the worn seal groove. i'm not trying to make the combustion chamber more detonation proof, i'm trying to make the cooling system leak proof. i know there is no valid way at this date to bulletproof the rotor seals, hence the reason that tuning is such an art in a rotary (nobody has the ***** to try it on their own). i just hate hearing about coolant seals failing because the driver in the car next to you farted too loud and the motor didn't like it. because from my understanding, these seals aren't just affected if you overheat, they like to blow if you sneeze too loud in your livingroom.

dopefishlives

That is the point. Remove one weakness, another weakness may show itself and you move on to resolving it as well. It is R&D and if you so wish to go that far, evolution, moving forward to improve.

I dont know how effective this idea would be but from the time I've spent with my motor it seems like a good idea.

Taking proper care of your coolant system and having a proper tune is a must either way, however why not improve upon something if the option to do so is there, instead of saying 'it will just resolve one problem and then you'll eventually find another'

_Kris

j9fd3s

iTrader: (3)

the difference between a rotary and a piston engine, is that the piston engine is blowing head gaskets due to detonation/preignition.

the rotary blows coolant seals due to overheating, or old age.

turbo blue

my idea was not to make the engine withstand more boost, detonation, or temperature. if the weak point in the cooling system is between the housings i would much rather change a radiator hose or a radiator cap or something external. i have always thought outside the box, and if a crappy little rubber seal bursts because it was extruded through a failure in the housing, i would see if i could find a more robust material (soft metal) to have a higher tendancy to stay in what is left of the machined groove. i'm not trying to make this motor bulletproof, thats an oxymoron, but if i could alleviate the need to tear down a perfectly healthy motor just to replace a piece of rubber that should have been better engineered to begin with, i will stop at nothing to make it work. like said before, i'm not trying to make a motor inpervious to failure, just trying to figure out a way to make a part that should never fail but does, less likely to do so. if i wanted to mess with a motor that was less suceptible to detonation, i sure to the world wouldn't have traded a 450 whp 240sx for an rx7. i know the risks and i know the consequences for just one little rattle, and i have no desire to mod the crap out of a rotary. i just want something to drive and be reliable, and if it requires me to tread on uncharted territory, i will.

a piece of rubber should never have even been considered as a reliable way to seal a vital internal component that must operate in conjunction with the combustion process. we know copper works for sealing the combustion area, i have seen it on the nasty top fuel dragsters. they don't use space age metals, just good ole copper headgaskets. it is easily formed (maleable) and can take a decent amount of heat, certainly more than a rubber seal. i just want to see if anyone else out there would see it from my point of view. if it worked well enough, you could eliminate the twin inner seals (one combustion and one coolant) or use them together for the bulls**t factor. i know the factory knows best for parts, but i hear of housing seals failing with no trace of overheating in sight, so maybe there is something better, just an idea.

turbo blue

nevermind. copper seal only works on a cylinder head because it is under a static squeeze. since the housings need to be perfectly flush a copper seal will crush and then be under no static pressure. myself and my buddy that's an aerospace engineer are going to start on finding a more suitable material and a process of testing (overheating ).

RETed

Try and PM banzaitoyota...
He had some super duper coolant seals using technology from nuclear reactors (or something like that) that ended up costing $100+ per seal.
If you're willing to spend the money, go for it.


-Ted

turbo blue

my motto is "an ounce of prevention is worth a pound of cure." i am still willing to research a cost effective way to better seal the combustion/cooling area. my engineering buddy and i might toy around with the idea, hopefully get some testing done, and maybe find a way to one up the factory engineers. i know trying to go above and beyond the factory is hard but i think mazda skimped a little when they used such an archaic method to seal vital engine components. i'll keep this updated and if something works out after some rigorous testing maybe it can happen. not sure if people would trust this, some are diehard "the factory knows best" people but if it turns out spectacular then i know at least i will use it.

splatterbass

it seems to me that a part of the problem to begin with is, that you have a seal in a groove squished to a flat surface. this inherantly allows for minimal distortion, as the seal is flexible. and will retain a seal with minor motion. as the seal moves into a gap trying to escape before the gasses. the idea of a copper crush ring is a good one, but might i sugjest that instead of mating it to a flat surface, place it in two grooves matched, with a rubber liner on the outside of the copper ( towards escape ). it seems to me this would offer a double redundancy towards faiure. in that, if the copper fails or is under over pressure and causes a coolant leak, you would only see that the next time you started the car and were burning the coolant that seeps into the combustion chamer during startup. once the seal is under load, than the copper would act as a piston to compress the rubber into the escape path, giving you time to get to work to afford a rebuild.
i could also see this as being a way to make the system stronger to allow probelems in the cooling system to be diagnosed and resolved without the need for a rebuild asap.
just a thought.
if you try it and it works. let me know.
may i sugjest using viton for the seals.
better at dealing with heat and chemicals than buna n, or other materials.

Gadd

It has been done. There are some old school builder/racers that used copper wire with a teflon insuation for a o ring. They would just put a dab of rtv at the joint.

j9fd3s

iTrader: (3)

while the coolant seals APPEAR to be unreliable, they will last 20years or 200,000miles if you dont overheat the car....

ive got 2 1st gens in my driveway, one is a 5/78 car with 91,000miles on it, the other is an 84 gsl-se with 251,000, they both have the original engines, neither one smokes, or uses oil or coolant....

the fd's get a bad rap, cause they just run too hot....

turbo blue

yes, hence the reason i did the fan mod with an aftermarket coolant gauge. i watch the temp gauge like a hawk and leave the fan switch on and allow proper time for warm up. I check the coolant daily, and oil as well. I have had to rebuild too many piston engines because someone didn't find it necessary to check the fluids on a regular basis. the metal coolant seal has been ditched for a more robust and less difficult rubber material with a special shape. the downside to this particular type of seal in question is it requires a super smooth machined groove be made where the existing o-ring groove used to be.